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My MB C300 will not start. I put the key in and turn it but nothing happens. The radio and internal lights do come on but not the car. The steering wheel is locked and can't put it on Neutral either (to push it out the garage).

Here is a list of troubleshooting steps that I tried (obtained from reading forums and calling around).

  1. Purchased a new battery assuming the root cause was the battery since it had a sticker date of 5/11 close to 5 years. Although the internal lights would come on and was able to lock and unlock the car (using main remote key) I thought it just did not have enough juice to crank the car. A new battery did not fix the issue.

  2. Tried turning the car on using the spare key. If the battery on your main remote key is low it can be the root cause for the car not starting (per local mechanic).

  3. Visually inspected all fuses and looked for a blown fuse, none found. I will be keeping this car for ever so I purchased a decent code scanner I can diagnose what the internal computer logs is giving out.

    • (5 days later) The scanner arrived, configured it for my car model. Ran diagnostic test, error results are as follows
    • A25407 (1/1) - The electronic steering lock has a malfunction. There is a mechanical fault.
    • A15F11 (2/2) - Relay 1 'Circuit 15R' has a malfunction. There is a short circuit to ground.
    • C01988 (1/2) - Interior CAN communication has a malfunction. CAN bus OFF default

    • B126231 (1/3) - No communication with the compass

    • B126322 (2/2) Compass: Signal amplitude too large
    • B127A54 (3/3) Compass: Incorrect calibration

I suspect the error keeping the car from starting are the A15F11 and A25407. This video shows the unit at fault. The car has to go to the dealer for repair since it will eventually require key programing something only dealers can do.

  • I would bet the car has lost the keys (no longer recognizes them for ignition purposes). Therefore it is seeing the keys as foreign and not allowing the signal to start the engine. Just a guess on my part as I don't know how the security system works for MB, but understand it's fairly funky. – Pᴀᴜʟsᴛᴇʀ2 Jun 1 '15 at 17:52
  • I can still lock and unlock the car, if it has lost the keys would it still be able to do that? – Geovani Martinez Jun 1 '15 at 19:21
  • I would think they are two separate systems and reading two separate things, but I don't know how MB has it setup. The only other thing I can think of is that the transponder (which is usually in the ignition area) is failing to work. It sends out s signal and when your key is close enough, the key is energized and sends back a signal to the receiver. If either side of this (transmitter/receiver) is not working, vehicle will not start. – Pᴀᴜʟsᴛᴇʀ2 Jun 1 '15 at 20:01
  • You are right Paul, both systems are separate. Just because I could lock and unlock the car did not mean I would be able to start it. The issue appears to be the steering column module, the unit that the key goes into. – Geovani Martinez Jun 17 '15 at 15:42
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I just repaired the identical car, the ignition does not come on and the wheels are locked and it sets steering column mechanical fault codes.

This means the solenoid that locks the column to stop the wheel turning is faulty, after it receives the unlock command from the electronic ignition switch it tells the ignition switch it is unlocked and then the ignition switch enables the ignition.

Mercedes won't sell these parts to anyone they say they are security items and you have to pay the dealer to install and code the modules.(Completely illegal!)

I found a company that if you send them the column and electronic ignition switch they remove the faulty solenoid and fit an emulator and program everything to work upon installation. You have to clear all the fault codes after. No more lock problem.

  • Do you have a name of the company? – George Mar 25 '16 at 21:58
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In MB, the ignition key is inserted into a component called EZS which is basically an ignition key control unit which also doubles as an immobilzer control unit. E ngine control unit, EZS, transmission control unit and electronic steering lock control unit are all part of the immobiliser system. Based on your symptoms with respect to shifting, steering and starting I guess the issue is with the ignition key control unit. Start checking the fuse. Connect the scanner and read the actual values. There are CAN messages from EZS to other control units which will give a hint. Also read the DTCs

  • I have done a visual inspection of the fuses, none appear to be blown. What you mention appears to be the root cause thou (from what I read on the forums etc..). I do not have a scanner, will get me one since I expect to use it in the future as well. What does DTCs stand for? I don't work on cars but using this opportunity to learn something new. – Geovani Martinez Jun 2 '15 at 16:40
  • DTC means diagnostic trouble code. When there is any issues in an electronically controlled system, a DTC is stored in the error memory of the corresponding control unit!!! – knocksAndMisfires Jun 2 '15 at 16:44
  • Thank you for the guidance. I purchased a code scanner (specifically for MB) and was able to get the DTCs being issued. I have listed them in the original question thread. It seems like the Steering Column Module is at fault. – Geovani Martinez Jun 17 '15 at 15:45
  • Cool. Terminal 15R is the power supply circuit that turns on when ignition key is in position 1. If that circuit has issue then there could be other symptoms also. There will be an ECU for steering column unit and you can read the actual values to see if they make sense. – knocksAndMisfires Jun 17 '15 at 18:21
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I'm not a mechanic nor claim to be Benz expert.. so just a suggestion if it helps in anyway.

I had issue 2-3 years ago starting my 2008 C300 after car battery replacement (from AutoZone). Somehow, I got it started few times, but at one point it did not start and I had to call in AAA. I initially thought it was battery related issue, but the AAA tech use to work for Benz Services got my car started in 10 seconds. He told me the car was in "Security Lockdown". He recommended following steps in order. (Note: Try Procedure 2 only if first one doesn't work.)

To unlock the security -

Procedure 1:

(1) Unlock the car, (2) Turn the key all the way without starting the car (3) Let the mirrors open up and everything to reset (~ 10 seconds) -- Should do this every time! (4) Start the car

Procedure 2:

If above doesn't work, here's a keyless entry option on the key:

(1) Press Unlock (2) Lock (3) Unlock (4) Lock (5) Lock (6) Unlock (7) Follow Procedure 1 steps above

I was told the Procedure 1 should be best practice for every day use as well!

Same issue happened to me 3 weeks ago after my car was sitting in driveway for 3 weeks. I searched internet for couple days trying to recall these steps, but could not find it anywhere! Luckily, I had documented above step and emailed it to myself.

Please spread this steps in other posts as I've read about similar symptoms I had reported. Again, it may not solve the ESI or other issues, but this is 10 second steps that may save lot of money and headache for people so please do pass it around.

Thanks

  • This actually worked for me one time. After a couple of days the same thing is happening. I tried the sequence, but with no success. Trying other things now. – Rcobrah Mar 28 at 0:55

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